Current Work

Examining chimerism and exploitation in Dictyostelium purpureum

Recent work has shown that genetically distinct clones of the social amoeba, Dictyostelium discoideum, collected from the wild can mix to form chimeras, and sometimes, one clone can exploit the other by contributing less than its proportional share to the sterile stalk (Strassmann, Zhu, & Queller 2000, Nature 408: 965-967).  I am currently exploring in another dictyostelid species (D. purpureum) whether genetically distinct clones of this species can also mix to form chimeras and if so, whether exploitation occurs. Dictyostelium purpureum varies slightly in parts of its developmental cycle compared to that of D. discoideum, and I am particularly interested in whether or not the delay in specialization that characterizes multicellularity in D. discoideum means that exploitation is diminished in species with earlier commitment to spore or stalk (e.g., D. purpureum)

Characterizing the cheating strategy of the developmental mutant chtA in Dictyostelium discoideum

I am examining the cheating strategy of a developmental knockout mutant called CheaterA (chtA or fbxA).  The chtA gene codes for a class of proteins involved in cell-fate decisions. In chimeras with wildtype cells, chtA cells preferentially form viable spores instead of dead stalk cells. This suggests that chtA should spread and disrupt cooperation in wild populations. We evaluated the behavior of chtA in chimeras with wildtype cells at low and high relatedness in order to characterize the costs and benefits of its cheating strategy, and to understand the conditions that favor its spread.

Documenting microsatellite variation in Dictyostelium discoideum

Using wild clones collected from five different geographical locations in the United States, I am genotyping more than 100 isolates at 5 microsatellite loci found to be polymorphic for this species.  Preliminary results indicate that there is substantial variation in the number of repeats across the various isolates for each of the 5 loci.

In addition to using this microbial system to study social evolution, I have also worked with social insects to examine cooperation, conflict, and coevolution in the attine ant-fungus symbiosis.  For more information, please visit http://www.biosci.utexas.edu/IB/faculty/mueller.htm

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